Cement placement tool and method



.2, 1969 J. K. BECKETT CEMENT PLACEMENT TOOL AND METHOD Filed Jan. 30,1968 n w mum w? m m nw HUI.

M VEIVTOA'. 4055 4 BETA/77 United States Patent 3,481,402 CEMENTPLACEMENT TOOL AND METHOD Joseph K. Beckett, Kern City, Calif., assignorto Gulf Oil Corporation, Pittsburgh, Pa., a corporation of PennsylvaniaFiled Jan. 30, 1968, Ser. No. 701,603 Int. Cl. E21b 33/ 13, 43/00 US.Cl. 166-290 12 Claims ABSTRACT OF THE DISCLOSURE Cement is placed at adesired interval in a well for displacement into the surroundingformation by placing the desired volume of a cement slurry in a tubingstring closed at its lower end and lowering the tubing string to thedesired level in the well. A closure member is secured to the bottom ofthe tubing string by means of left-hand This invention relates to amethod and apparatus for depositing cement or other sealing or pluggingmaterial at a desired interval in a well to prevent flow of undesirablefluids into the well.

Frequently excessive amounts of water are produced with oil produced byan oil well. If the water is flowing into the well from isolatedintervals penetrated by the well, the difliculty can be remedied byplugging the formation through those intervals. The usual method ofplugging isolated intervals has been to lower a dump bailer containing aliquid plugging material such as a slurry of a hydraulic cement, usuallyPortland cement, suspended from wire line into the well to the depth ofthe interval to be plugged. After the dump bailer is at the desiredlevel in the well, the bailer is opened to discharge the cement into thewell. The cement is forced through perforations in casing, if the wellis cased through the interval producing the undesired fluids, ordirectly into the formation through the interval if the well has beencompleted with an open hole.

Some difficulty has been encountered in discharging the cement slurryfrom the dump bailer. One method of overcoming that difiiculty has beento include within the dump explosive charges which are ignited after thebailer is at the desired level in the well. The explosive forces thecement slurry out of the bailer. One of the disadvantages of dumpbailers, both of the explosive-discharging type and the ordinary typewhich does not use an explosive to discharge the cement, is prematuredischarging of the cement from the bailer. If a bailer having its lowerend closed, for example by having a frangible disc or other mechanismactuated by a blow, strikes a liner or other obstruction in the well,the bailer may be unloaded before it has reached the desired level.Moreover, the limited volume of bailers of a size that can beconveniently used requires repeated trips into the well. Frequentlydiscontinuous plugs are formed through the interval to be pluggedbecause of the intermittent type of operation.

This invention resides in a method and apparatus for plugging a selectedinterval of a well in which a cement slurry or other fluid capable ofbeing forced into the formation at the selected interval to form thedesired plug is delivered to the interval to be plugged in tubing havingat its lower end a detachably secured closure mem- "ice her. A column ofliquid is in the tubing above the cement slurry. The tubing is thendisconnected from the closure member at the level to be plugged to allowflow of the plugging material from the tubing. A swab cup on the tubingstring just above the connection of the tubing string to the closuremember confines the plugging material to the desired interval. Theclosure member is suspended from the lower end of the tubing afterdisconnecting to allow the closure member to be withdrawn from the well.

In the drawings:

FIGURE 1 is a diagrammatic side view, partially in vertical section, ofthe tool used in the method of this invention.

FIGURE 2 is a diagrammatic view of a well as the tool is lowered intothe desired location in the well.

FIGURE 3 is a diagrammatic illustration of the tool in place before theplugging material is discharged from the tool.

FIGURE 4 is a vertical sectional view of the well showing the tool at anintermediate position during the discharge of the plugging material.

Referring to FIGURE 1 of the drawing, the tool is illustrated secured tothe lower end of a tubing joint 10 by a coupling 12. Coupling 12 isinternally threaded for connection to the tubing joint 10 and to atubing nipple 14. Coupling 12 is also externally threaded on the lowerend to receive a downwardly opening swab cup 16.

A lower coupling 18 is internally threaded at its upper end forconnection to the lower end of nipple 14. Lower coupling 18 is threadedat its lower end with left-hand threads 20 to receive left-hand threadson a suitable closure member. In the embodiment of the inventionillustrated in the drawing, the closure member is a bull plug 22 havinga left-hand threaded pin 24 at its upper end for engagement withinternal left-hand threads in the lower end of coupling 18.

A belly spring indicated generall by 30 has an upper collar 32 and alower collar 34 joined by a plurality of bowed strips 35 adapted toengage the borehole wall if the well is completed open-hole, or toengage the casing of a cased well, to prevent rotation of the bellyspring when the drill string is rotated. Upper collar 32 is slidable onnipple 14 between the coupling 18 and swab cup 16. Lower coupling 18serves as a stop limiting downward movement of collar 32 to permitremoval from the well of the closure member after it has beendisconnected from the lower coupling 18, as hereinafter described. A pin26 extends transversely through the bull plug 22 and is secured theretoby any suitable means such as welding or a friction fit. Both ends ofpin 26 extend outwardly beyond the bull plug 22 and through holes 28 inlower collar 34. Holes 28 have a diameter slightly larger than thediameter of pin 26 to provide a loose fit aiding in alignment of thelefthand threads as the tool is assembled. Collar 34 can be hinged orconstructed in two parts that are secured together after placement overthe pin 26.

The method and apparatus of this invention will be described forplugging the formation surrounding perforations 36 in the casing 38 of awell illustrated in FIGURES 2, 3 and 4 of the drawing. The perforations36 are in an interval through which undesired fluids, ordinarily water,flow into the well. .In many instances the perforations may extendwithout interruption from the water-bearing formation to be plugged intoan overlying oil-bearing formation. The tool and method of thisinvention can be used for setting a plug through such water-bearingintervals as well as through the entire perforated interval. Theformation to be plugged may be at any level in the well, but forsuccessful plugging of undesirable fluids without an adverse elfect onthe production of desirable fluids, it is preferred that the formationto be plugged be isolated from the formations producing the desiredfluids.

The tool is made up as illustrated in FIGURE 1 and connected to thelower joint of a tubing string indicated by reference numeral 40 inFIGURES 3 and 4. Tubing string 40 has a spring-loaded, downwardlyopening check valve 42 mounted therein at a level below the level ofliquid in the well at the end of the displacement of cement from thetubing string, as illustrated in FIGURE 3. The amount of cement slurryestimated to be required to plug effectively the water-producinginterval is placed in the tubing string. Filling can best beaccomplished by making up the tool and tubing string up the check valve42 and lowering the tool into the well as it is made up. The tubingstring is filled with cement slurry, the check valve is installed, andthe tubing is made up to a length such that its internal volume is equalto the total volume of cement to be displaced into the well. That lengthof tubing string is lowered into the well as it is made up and thenfilled with a cement slurry. Making up of the tubing string is thencontinued and the tubing string run into the well to fix the level ofthe tool illustrated in FIGURE 1 at the level of perforations 36, asshown in FIGURE 3 of the drawing.

After the lower end of the tubing string is at the desired level, awater or oil column is placed in the tubing string above the cement to alevel such that when the cement is discharged from the tubing string theliquid level within the tubing string will be substantially the same asthe liquid level in the annulus between the tubing string and thecasing.

With the tool at the level shown in FIGURE 3, the tubing string isrotated to the right. The friction of the belly spring 30 against thecasing 38 prevents rotation of the belly spring. Engagement of collar 34with pin 26 prevents rotation of bull plug 22; hence, the bull plug 22is unscrewed from lower collar 18 on continued rotation of the tubingstring. Bull plug 22 is then suspended from the lower end of tubingstring by means of the belly spring 30 and the engagement of collar 32with lower coupling 18 and of collar 34 with pin 26. Upward fiow of thecement slurry through the annulus surrounding tubing string 40 isprevented by swab 16.

After flow of cement from the tubing string has started, the tool isgradually raised to position the swab cup 16 above the uppermost ofperforations 36. The column of liquid in the tubing string above thecement slurry forces the cement slurry outwardly into the borehole andthrough the perforations 36 into the formation. After the cement hasequalized, the tubing string is lowered rapidly to provide a vigorousdown-swab action. The swab cup 16 increases the pressure forcing thecement into the formation to be plugged without applying additionalpressure on the liquid in the annulus overlying the cement; hence, theoverlying liquid is not forced through the perforations 36. Upwarddisplacement of the cement slurry through the tubing string 40 duringthe lowering of the cup is prevented by spring-loaded check valve 42.

At the end of the operation, the liquid level 44 in the annulus betweenthe casing 38 and tubing string 40 will be substantially the same as theliquid level 46 within the tubing string. If desired, liquid can beintroduced into the annulus to wash cement from the upper surface of theswab cup and increase the pressure available to force the cement slurrythrough the perforations 36 into the formation. The tubing string isthen pulled from the Well. Engagement of collar 32 with coupling 18 andattachment of collar 34 to bull plug 26 causes the bull plug to beremoved from the well with the tubing string.

If the zone to be plugged is contiguous to a potentially oil-producingzone and the perforations continue into the potentially oil-producingzone, the tubing string 40 is raised only to place the swab cup at theupper limit of the zone to be plugged. The swab cup then prevents flowupwardly into the perforations in the oil-producing zone.

Plugging intervals of a well by this invention allows a substantialreduction in the cost of setting a plug as compared with theconventional dump bailer or explosiveoperated discharge bailertechnique. This invention is particularly advantageous when largevolumes of plugging materials are required to plug the desired interval.A continuous plug can be laid in the hole without potential skips orcavities that occur between runs of sequential small loads. Thedisconnection of the closure member to allow flow from the tubing stringis much less likely to discharge the plugging material prematurely thanfrangible discs or slide valves in tubing strings or the explosive dumpbailer.

This tool and method also eliminate the shortcoming of pumping smallplugs into a well with regular surface cementing pump and equipmentwhere the pressure in the formation will not support the hydrostatichead of liquids the full height of the well casing. Those excessiveliquid heads will often squeeze the cement out into the formation wellbeyond desired limits. This tool can place a slurry in any shallow wellwith any low liquid level without increasing the hydrostatic level inthe well excessively. The actual liquid rise need only be that caused bythe liquids that are placed inside the tubing for the purpose ofassuring proper equalization of the cement slurry.

I claim:

1. A method of plugging a formation penetrated by a well comprisinglowering a tubing string in the well to place the lower end of thetubing string at the level of the formation to be plugged, filling thetubing string with the desired volume of a liquid plugging material,disconnecting the lower end of the tubing string, displacing the liquidplugging material from the tubing string at the level of the formationto be plugged, blocking upward flow around the tubing string to directthe plugging material displaced from the tubing string into saidformation, and thereafter withdrawing the tubing string and disconnectedlower end from the well.

2. A method as set forth in claim 1 in which the plugging material is aslurry of hydraulic cement.

3. A method as set forth in claim 1 in which pressure is applied to thecement in the borehole of the Well but not to liquid overlying thecement to displace the cement into the formation to be plugged.

4. A method as set forth in claim 1 wherein the closure member isconnected to the lower-end of the tubing string by a left-hand thread topermit disconnecting the closure rnember from the tubing string, and adownwardly openmg swab cup counted on the lower end of the tubing strlngabove the left-hand thread blocks upward fiow through the annulussurrounding the tubing string.

5. A method as set forth in claim 4 including the steps of engaging thewall of the well with means secured to the closure member and turningthe tubing string to unscrew the closure member therefrom.

6. A method of plugging a formation penetrated by a well having liquidstanding therein above the level of the formation comprising placing thedesired volume of a cement slurry in a tubing string closed at its lowerend by a closure member, placing a column of liquid of a height locatingthe upper surface thereof at substantially the level of the liquid inthe well at the end of the plugging operation, lowering the tubingstring in the well to place its lower end at the level of the formationto be plugged, disconnecting the closure member from the lower end ofthe tubing string whereby the column of llqllld in the tubing stringdischarges the cement slurry therefrom.

7. A method as set forth in claim 6 in which upward flow of liquidaround the tubing string after disconnecting the closure member isblocked to direct the cement slurry into the formation.

8. A method as set forth in claim 6 in which the tubing string is movedslowly upwardly through the interval to be plugged to the upper limit ofthe interval after disconnecting the closure member.

9. Apparatus for plugging a formation penetrated by a well with a fluidplugging material comprising a tubing string, a closure member securedto the lower end of the tubing string by a left-hand thread whereby theclosure member can be disconnected from the tubing string on rotation ofthe tubing string to the right, friction means secured to the closuremember and adapted to engage the borehole wall, and means connecting theclosure member to the tubing string for limiting movement of the closuremember apart from the tubing string on disconnection of the closuremember from the tubing string.

10. Apparatus as set forth in claim 9 in which a downwardly opening swabcup is mounted on the tubing string near the lower end thereof but abovethe connection of the closure member to the tubing string.

11. Apparatus as set forth in claim 10 in which a check valve mounted inthe tubing string prevents upward flow therethrough.

12. Apparatus for plugging a selected formation penetrated by theborehole of a well comprising a tubing string, a closure memberconnected to the lower end of the tubing string by a left-hand thread, acollar vertically slidable on the tubing string above the left-handthread,

stop means limiting downward movement of the collar on the tubingstring, outwardly bowed members adapted to engage the wall of the wellsecured at their lower ends to the closure member and at their upperends to the collar, and a downwardly opening swab cup mounted on thetubing string adjacent and above the collar adapted to engage the wallof the well to prevent upward flow through the annulus surrounding thetubing string.

References Cited UNITED STATES PATENTS 1,971,514 8/ 1934 Stone 166-1242,189,445 2/1940 Dale l661 17 2,191,702 2/ 1940 Yowell 166---272,493,962 1/ 1950 Gray 166-27 2,671,511 3/1954 Mater 166-226 JAMES A.LEPPINK, Primary Examiner U.S. Cl. X.R. 166166, 226

